Flupyradifurone-based insecticide influences foraging behaviour but does not alter chemosensory orientation of Bombus terrestris

In recent decades, pollinating insect populations have drastically declined, partly due to the extensive use of various agrochemicals. Flupyradifurone is a systemic butanolide insecticide that has been considered to pose low risk to bees; however, recent studies have shown that it can cause various sublethal effects (e.g. reduced learning ability and memory) in various pollinators. In this study, we examined how exposure to a flupyradifurone-based insecticide formulation for 1, 2, or 3 weeks affected peripheral olfactory detection of a synthetic floral blend and the foraging behaviour of buff-tailed bumblebee ( Bombus terrestris ) workers. We found that pesticide-treated bumblebees approached the two visually cued target locations (scentless or scented with the floral blend) significantly less frequently, but they did not choose the floral blend at a lower rate than the control animals did. The latency to first approach a target location also differed between treatment groups as pesticide-treated bees reached the first location with a 37% lower probability than control animals at any time during the behavioural trial. The antennal response of bumblebees was dose-dependent, but time also modulated its magnitude at higher doses, and this effect was observed in both control and treated individuals. Overall, exposure to a low concentration of flupyradifurone altered some aspects of bumblebees’ foraging behaviour regardless of exposure length, but did not influence their chemosensory perception or orientation. Future investigations should examine whether these sublethal effects identified at the individual level may scale up to impair colony growth or reproductive output in this important pollinator species.